The present invention relates to electronic keys, and to integrated circuits which provide electronic key functionality.
An electronic key is a circuit which performs the function of a key, using stored information instead of shaped metal. Such keys, and related circuits, have found use in a wide variety of applications.
However, electronic keys present some unusual difficulties in design. There is always some risk that an intruder may obtain a key and attempt to "crack" it, to gain free access to the system which is supposed to be protected. Thus, although perfect security may not be possible, the design must provide as much security as is economically possible.
The present application, and the parent applications, disclose a number of innovations which cooperate together to provide a greatly improved electronic key.